The Orzeł class was a short series of modern submarines built in Dutch shipyards for the Polish Navy in the 1930s. Four submarines were planned but only two were completed. They saw service during World War II.
Initially the design was to be built in the United Kingdom, but the price proposed was too high and the British Admiralty announced that building a fast submarine with over 20 knots (37 km/h) of surface speed was technically impossible. The two submarines were ordered in De Schelde and Rotterdamse Shipyards, ORP Orzeł(Eagle) and ORP Sęp(Vulture) (four were initially planned). Design was made in cooperation with a team from Polish Navy, and incorporated some features of the earlier Dutch submarine HNLMS O 16 including the external trainable mount. The hull was entirely welded, and all controls were hydraulically operated. The design was made to fulfill the Polish requirements for a multi-purpose vessel, to be used both in the shallow waters of the Baltic Sea and in the high seas. They were among the most modern submersibles in the Allied fleets at the outbreak of World War II. Their speed was 19.5 knots (36 km/h). This class of submarine was the basis for next Dutch O 19-class submarines.
Orzeł was ordered in 1935 and commissioned in February 1939. On 14 September 1939 Orzel and Wilk(Wolf) were ordered to make for British ports. Wilk arrived on 20 September 1939 and Orzeł arrived on 14 October 1939 (after an adventurous voyage with no charts). On 8 April 1940 Orzeł sank two large troop transports at the start of the German invasion of Norway. Orzeł was lost with all hands due to unknown reasons while on patrol in North Sea. Orzeł 's loss is one of the biggest mysteries in Polish naval history.